Function runDockerInspect

agent/agentcontainers/containers_dockercli.go:313–339

runDockerInspect is a helper function that runs `docker inspect` on the given container IDs and returns the parsed output. The stderr output is also returned for logging purposes.

(ctx context.Context, execer agentexec.Execer, ids ...string)

// container IDs and returns the parsed output.
// The stderr output is also returned for logging purposes.
func runDockerInspect(ctx context.Context, execer agentexec.Execer, ids ...string) (stdout, stderr []byte, err error) {
	if ctx.Err() != nil {
		// If the context is done, we don't want to run the command.
		return []byte{}, []byte{}, ctx.Err()
	}
	var stdoutBuf, stderrBuf bytes.Buffer
	cmd := execer.CommandContext(ctx, "docker", append([]string{"inspect"}, ids...)...)
	cmd.Stdout = &stdoutBuf
	cmd.Stderr = &stderrBuf
	err = cmd.Run()
	stdout = bytes.TrimSpace(stdoutBuf.Bytes())
	stderr = bytes.TrimSpace(stderrBuf.Bytes())
	if err != nil {
		if ctx.Err() != nil {
			// If the context was canceled while running the command,
			// return the context error instead of the command error,
			// which is likely to be "signal: killed".
			return stdout, stderr, ctx.Err()
		}
		if bytes.Contains(stderr, []byte("No such object:")) {
			// This can happen if a container is deleted between the time we check for its existence and the time we inspect it.
			return stdout, stderr, nil
		}
		return stdout, stderr, err
	}
	return stdout, stderr, nil
}

// To avoid a direct dependency on the Docker API, we use the docker CLI
// to fetch information about containers.